title: Rh-catalyzed asymmetric hydrogenation of unsaturated lactate precursors in propylene carbonate.
abstract: The asymmetric hydrogenation of alpha-acetoxy acrylates to O-acetyl lactates with Rh catalysts based on chiral bisphospholane ligands was investigated in propylene carbonate (PC) as "green" solvent. In contrast to DuPHOS-type ligands, catASium M ligands lead to full conversion of the substrate in PC and induce excellent enantioselectivities for ethyl ester and methyl ester substrates (>98 %). Moreover, the undesired opening of the maleic anhydride moiety of the catASium M ligand observed in MeOH can be prevented under these conditions. The chiral product can be easily separated from the carbonate solvent by distillation. In this way, an ecologically benign process for the production of enantiopure lactic acid derivatives was established which offers a highly efficient catalytic transformation in a green solvent under mild conditions (1-10 bar H(2)).
authors.affiliation: Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein Strasse 29a, 18059 Rostock, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schäffner
authors.forename: Vasyl
authors.initials: V
authors.lastname: Andrushko
authors.forename: Jens
authors.initials: J
authors.lastname: Holz
authors.forename: Sergey P
authors.initials: SP
authors.lastname: Verevkin
authors.forename: Armin
authors.initials: A
authors.lastname: Börner
mesh_terms: D002384:Catalysis; D055772:Green Chemistry Technology; D006865:Hydrogenation; D019344:Lactic Acid / Q000737:chemistry*; D008024:Ligands; D011407:Propane / Q000031:analogs & derivatives* / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D008024:Ligands; D012997:Solvents; D019344:Lactic Acid; C045990:propylene carbonate; D012238:Rhodium; D011407:Propane